Glazing Is the Riskiest Step
Of all the stages in pottery, glazing involves the greatest variety of potentially hazardous materials. Commercial glazes are largely safe when used correctly, but understanding the risks allows you to work confidently and protect yourself.
The Main Hazards
Heavy Metal Oxides Many glaze colorants contain metal compounds: cobalt carbonate for blue, copper oxide for green, manganese dioxide for brown, iron oxide for amber. In their raw form these are fine powders that must not be inhaled or ingested.
- Manganese in particular has well-documented neurological effects from chronic inhalation.
- Barium carbonate (sometimes used as a flux) is toxic if ingested.
- Lead is now rarely used in studio pottery but occasionally appears in vintage glaze recipes; never use lead-based glazes.
Silica Dust Raw glaze materials like silica, feldspars, and whiting are silica-bearing powders. Inhaling fine silica particles causes silicosis, the same risk as clay dust.
Skin Absorption Some metal compounds absorb through the skin over time, particularly with prolonged repeated exposure.
The Good News
Commercial pre-mixed glazes come in liquid suspension. The hazardous particles are locked in the liquid, dramatically reducing inhalation risk. The main precautions are:
- Do not eat or drink while glazing.
- Wash hands thoroughly after each session.
- Wear gloves if using raw oxide powders.
- Never dry-mix glaze powders without a respirator.
Safety Checklist for Glaze Sessions
Before you start:
- Containers labelled with contents and cone range
- Nitrile gloves and respirator ready if powders are involved
- No food or drinks anywhere near the glazing area
Treat glazing like lab work – simple prep keeps you safe long term.
The Bigger Picture
The lung disease caused by inhaling fine silica particles is called silicosis, a serious occupational hazard for potters who mix dry materials without protection. Many glaze colorants are metal compounds, and the Wikipedia article on manganese dioxide details the chemistry behind one of the most hazardous pigments used in brown and black glazes.
Common Mistakes and Quick Fixes
- Mixing powders bare-faced for “just one minute”: Put the respirator on before opening the bag, not after dust is already in the air.
- Using food containers for glaze storage: Keep all glaze materials in clearly labelled, dedicated studio containers only.
- Ignoring small skin exposure: Repeated minor contact adds up. Gloves and immediate hand washing are the long-term protection.
- Assuming “natural” equals harmless: Many naturally occurring minerals are still hazardous when inhaled as fine dust.
Studio Drill
Run a five-minute safety setup drill before your next glaze session. Lay out PPE, check labels, clear food and drink, and rehearse your cleanup plan. If this feels slow at first, that is normal. After a few sessions it becomes automatic, and you reduce risk without sacrificing momentum.
